The latest kernels released by all the main distros have fortunately fixed most of the compatibility problems with our NC10.
One of them was the ALSA driver that did not properly detect the audio card, with the result that the external speakers were not disabled when an headphone was inserted.

However, there is a little problem yet: the FN-F6 key does not really mute/unmute the audio, even if the graphical popup says so.

The problem is not critical because we can always set the audio level with FN-Left and FN-Right keys, and if you want you can ignore it while waiting for it to be "automatically" fixed with future official updates from Ubuntu.

Anyway, we are here to solve problems, so here is the solution.
We'll install ALSA module taken directly from the next to-be-released Ubuntu 9.04.

Let's go on Ubuntu site, download the ALSA source package (look at the bottom of the page for the link) and install it.

Now we have the sources; we have to compile them.
For this task we can use module-assistant, a great tool for managing external kernel modules. It's exactly what we need.
Install it, then run it with admin rights

and its simple textual (but very useful) menu will show up in your terminal.

The first thing to do is to move on UPDATE to update the cached packages information.
Then, move on PREPARE to install all the needed stuff for compiling kernel modules.

Now we can start to work on ALSA modules.
Move on SELECT and a new menu will appear. Select "alsa" from the list then select OK (a little note: you can move the cursor between the list and the OK-Cancel buttons with the TAB key).

A new menu will appear with various options for the selected module. Move on BUILD. The build process will take some time (minutes) to complete, so do something else while waiting for it .

When it's done, module-assistant will ask you if you want to install the new just-created package, select YES (or select NO then select INSTALL option in the main menu).
We are done. Select BACK/Cancel/Quit in all the menus to quit modules-assistant and restart your NC10 to finally have a working FN-F6 key.

PS:
You have to repeat the module installation for any new future kernel you will install.
It's not that hard: just launch again module-assistant, select "alsa" from the modules list and rebuild/reinstall it.

I've just run across a rather weird problem. For some reason, the volume function keys do not actually control the volume. The osd display shows increase/decrease/mute (so the keys themselves do work), but the sound is not affected by it. I already tried all the different available options in the gnome-volume-control preferences. Any ideas?